The Universe is Expanding The redshifts of galaxy superclusters increase with distance Doppler shifts from spectra and distance from Cepheids were used to derive "Hubble's Law" Recessional Velocity = H0 X distance The value of the Hubble Constant, H0, is approximately the inverse of the age of the universe.

Other Standard Candles Probe the Far Distant Universe Tully-Fisher relation - "The broader the HI line, the brighter the galaxy" - due to higher Keplerian Velocities in bigger/brighter galaxies Supernovae These results confirm the expansion of the universe Einstein's theory of general relativity predicted the universe could not be static, but he doubted this, so he added a cosmological constant to counter the attractive force of gravity. The discovery that the universe was expanding made this appear to be a mistake Einstein's "biggest blunder" turns out to be approximately correct, however, since we find that the universe is accelerating outwards.

The Cosmological Redshift is Due to Expanding Space The Red-Shifts of distant galaxies are not just because Galaxies are receding The reddening of photons is a result of the expansion of Space-Time as predicted by Einstein's Theory of General Relativity

Fossil Radiation from the Big Bang is Observed Today! By re-winding the tape of the expanding universe, we see the cosmos was initially in a very hot, dense state! The universe was opaque (photons couldn't travel far) before it cooled enough for electrons to reside in atoms. Radiation from the opaque period reaches us now from over 13 billion light years away and is highly red-shifted. This Cosmic Microwave Background radiation was discovered by accident in the 60's. The CMB radiation exhibits a Planck Black-Body distribution associated with a temperature of about 3 K.

Small-scale Fluctuations of the CMBR tell us about the Universe COBE was the first to detect variations Since then, WMAP has done the best job of measuring the tiniest fluctuations.

Theories of the Four Forces indicate that they all behave as one at very high temperatures All forces were unified in the early universe As the universe cooled, this "symmetry" was broken and the forces emerged independently one at a time

The CMBR is Smoother than Expected If the expansion was the same in the past, then there would be large temperature fluctuations observed in the CMBR This is the "isotropy problem" The smoothness of the CMBR could have been produced if the universe expandedly very rapidly early on during the Inflationary Epoch This could have happened if the universe rapidly expanded from a false vacuum to a true vacuum

The Universe changed from being controlled by radiation to matter Within the First Three Minutes - Free Neutrons decayed so that there was an excess of protons over neutrons When it was cool enough for Helium nuclei to form, nearly all the remaining neutrons went into He, setting the H/He ratio (plus a little Lithium) to what we observe today Heavier Nuclei did NOT FORM in the Big Bang Up until 30,000 years after the beginning, the energy density of the universe was dominated by photons - this kept matter from collapsing During the first 500,000 years, photons prevented the recombination of electrons and nuclei to form neutral atoms.

The Universe Became Transparent during the Era of Recombination Free Electrons look "bigger" to photons and can more easily intercept them Electrons in atoms are less obvious to photons, which then can travel long distances Freely traveling photons indicate a transparent universe

The Observable Universe is Finite Since the Universe is about 14 billion years old, we can't see further away than about 14 billion LY This distance marks the boundary of a sphere known as the cosmic light horizon

Astronomers Calculate the Early Rate of Star Formation Based on Galaxy Luminosities As we look back in time, galaxies are forming by the accretion of small proto-galaxies The Early Star-formation Rate determines what kind of a galaxy is formed A rapid burst of star formation uses up all the gas before a disk forms and yields an elliptical galaxy Slowly Forming Stars settle into a spiral-galaxy w/disk before the gas is used up.

Future Space Telescopes will probe further back into the "Dark Ages" of the Early Formation of the Universe

The Density of the Universe Determines its Fate The gravitational attraction of light and dark matter must be balanced against the repulsive force of dark energy to determine if the universe will expand for ever, or slow down and fall back upon itself A flat universe extends without limit and will not fall back on itself - Parallel light rays remain parallel in this universe and space is not curved but "Flat" A "closed" universe will fall back on itself - Parallel light rays converge as do longitude lines at the poles. An "open" universe will extend without limit; parallel light rays will diverge. The scale of fluctuations in the microwave background gives a key to the curvature of space-time

Distant Supernovae show that the Universe is Accelerating! Deviation from the Hubble Law at great distances shows a different expansion rate at past times "Dark Energy" may be the cause "Quintessence," is another theoretical idea for the apparent acceleration